Hi, I ran into a simple problem which puzzled me in GMT. It says that for MSK, the modulation index used (h) = 0.5 in other words, the minimum frequency difference of the two frequencies used are F1-F2=1/2T (I hope this refers to the bit Duration, I am confused here too).

My problem is that I have not seen any proper reasoning why this is so(x=0.5). With some searching I only found that this requirement for the frequency orthogonal over one bit interval. Most of the documents state it as an obvious statement.